refactor: got rid of gcc-9 backlog

BREAKING CHANGE: gcc-9.3 no longer supported

docs/CHANGELOG.md

@@ -1,7 +1,7 @@
 # Release notes
 
 - **0.6.0 WIP**
-  - Minimum compiler version supported changed to gcc-9.3
+  - gcc-9 is no longer supported (at least gcc-10 is required)
   - MSVC 16.7 support added
   - linear_algebra updated to 0.7.0/stable
   - fmt updated to 7.0.3

docs/design/quantity.rst

@@ -44,7 +44,7 @@ a few additional member types and functions::
 
     template<typename D1, typename U1, typename Rep1, typename D2, typename U2, typename Rep2>
       requires detail::basic_arithmetic<Rep1, Rep2> && (!equivalent_dim<D1, D2>)
-    [[nodiscard]] constexpr Quantity AUTO operator/(const quantity<D1, U1, Rep1>& lhs,
+    [[nodiscard]] constexpr Quantity auto operator/(const quantity<D1, U1, Rep1>& lhs,
                                                     const quantity<D2, U2, Rep2>& rhs);
 
 Additional functions provide the support for operations that result in a

docs/index.rst

@@ -16,7 +16,7 @@ with a permissive `MIT license <https://github.com/mpusz/units/blob/master/LICEN
 .. note::
 
     As this library targets C++23 and extensively uses C++20 features as of now it compiles correctly
-    only with gcc-9.3, MSVC 16.7, and newer.
+    only with gcc-10, MSVC 16.7, and newer.
 
 .. toctree::
     :maxdepth: 2

docs/usage.rst

@@ -4,7 +4,7 @@ Usage
 .. note::
 
     This library targets C++23 and extensively uses C++20 features that is why, as of now, it compiles correctly
-    only with gcc-9.3, MSVC 16.7, and newer.
+    only with gcc-10, MSVC 16.7, and newer.
 
 Repository Structure and Dependencies
 -------------------------------------
@@ -17,8 +17,6 @@ This repository contains three independent CMake-based projects:
   - when this library will become part of the C++ standard it will have no external dependencies
     but until then it depends on:
 
-    - `range-v3 <https://github.com/ericniebler/range-v3>`_ (only for gcc versions < 10.0) to provide
-      C++20 concepts library definitions.
     - `{fmt} <https://github.com/fmtlib/fmt>`_ to provide text formatting of quantities.
     - `ms-gsl <https://github.com/microsoft/GSL>`_ to verify runtime contracts with `Expects` macro.